npiet: add package tests

pkgs/by-name/np/npiet/package.nix

@@ -7,6 +7,7 @@
   groff,
   libpng,
   tk,
+  callPackage,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -38,6 +39,19 @@ stdenv.mkDerivation (finalAttrs: {
 
   strictDeps = true;
 
+  passthru.tests =
+    let
+      all-tests = callPackage ./tests { };
+    in
+    {
+      inherit (all-tests)
+        hello
+        prime
+        no-prime
+        brainfuck
+        ;
+    };
+
   meta = {
     description = "Interpreter for piet programs. Also includes npietedit and npiet-foogol";
     longDescription = ''

pkgs/by-name/np/npiet/tests/default.nix

@@ -0,0 +1,41 @@
+{ fetchurl, callPackage }:
+let
+  # More examples can be found at https://www.dangermouse.net/esoteric/piet/samples.html
+  hello-program = fetchurl {
+    url = "https://www.dangermouse.net/esoteric/piet/hw6.png";
+    hash = "sha256-E8OMu0b/oU8lDF3X4o5WMnnD1IKNT2YF+qe4MXLuczI=";
+  };
+  prime-tester-program = fetchurl {
+    url = "https://www.bertnase.de/npiet/nprime.gif";
+    hash = "sha256-4eaJweV/n73byoWZWCXiMLkfSEhMPf5itVwz48AK/FA=";
+  };
+  brainfuck-interpreter-program = fetchurl {
+    url = "https://www.dangermouse.net/esoteric/piet/piet_bfi.gif";
+    hash = "sha256-LIfOG0KFpr4nxAtLLeIsPQl+8Ujyvfz/YnEm/HRoVjY=";
+  };
+in
+{
+  hello = callPackage ./run-test.nix {
+    testName = "hello";
+    programPath = hello-program;
+    expectedOutput = "Hello, world!";
+  };
+  prime = callPackage ./run-test.nix {
+    testName = "prime";
+    programPath = prime-tester-program;
+    programInput = "2069";
+    expectedOutput = "Y";
+  };
+  no-prime = callPackage ./run-test.nix {
+    testName = "no-prime";
+    programPath = prime-tester-program;
+    programInput = "2070";
+    expectedOutput = "N";
+  };
+  brainfuck = callPackage ./run-test.nix {
+    testName = "brainfuck";
+    programPath = brainfuck-interpreter-program;
+    programInput = ",+>,+>,+>,+.<.<.<.|sdhO";
+    expectedOutput = "Piet";
+  };
+}

pkgs/by-name/np/npiet/tests/run-test.nix

@@ -0,0 +1,19 @@
+{
+  runCommand,
+  lib,
+  npiet,
+
+  testName,
+  programPath,
+  programInput ? "",
+  expectedOutput,
+}:
+runCommand "npiet-test-${testName}" { } ''
+  actual_output="$(echo '${programInput}' | '${lib.getExe npiet}' -q -w -e 100000 '${programPath}')"
+  if [ "$actual_output" != '${expectedOutput}' ]; then
+    echo "npiet failed to run the program correctly. The output should be ${expectedOutput} but is $actual_output."
+    exit 1
+  fi
+  echo "The program successfully output $actual_output"
+  touch "$out"
+''